In the automatic testing of integrated circuits (IC) and other electronic devices, special machines, referred to hereinafter as “peripherals,” have been used which place the device to be tested in position for testing by an automatic testing system. Peripherals include wafer probers, package handlers, and the like; the specific type of peripheral utilized is dependent upon the stage of production where it is used. The electronic testing itself is provided by a large and expensive automatic testing system which includes a test head which has been required to connect to and dock with the peripheral. In such testing systems, the test head has been usually very heavy—on the order of 40 to 1000 kilograms. The reason for this heaviness is that the test head uses precision high speed electronic timing signals as well as other data signals, which requires that the electronic circuit must be located as close as possible to the device under test. Accordingly, the test head has been densely packaged with electronic circuits in order to achieve the high speed testing of the sophisticated devices.
Test head positioner systems may be used to position the test head with respect to the peripheral. When the test head is accurately in position with respect to the peripheral, the test head and the peripheral are said to be aligned. When the test head and the peripheral are aligned, the fragile test head and peripheral electrical connectors can be brought together (i.e., docked), enabling the transfer of test signals between the test head and the peripheral. Prior to docking, the fragile test head and peripheral electrical connectors must be precisely aligned to avoid damaging the fragile electrical connectors.
In order to enable such precise alignment of fragile electrical connectors, electronic test head positioners typically facilitate maneuvering the test head through space with six degrees of freedom. As shown in FIG. 9, six degrees of motion are defined. The positioner system in accordance with an exemplary embodiment of the present invention accomplishes these six degrees of motion. FIG. 9 illustrates left-right motion or motion along the X axis; up-down motion or motion along the Y axis; in-out motion along the Z axis; motion about the Y-axis or theta motion; motion about the X-axis or pitch motion; and motion about the Z-axis or roll motion.
Further, test head positioners also typically provide a substantially weightless or compliant condition to the test head so that the test head may be manipulated by hand for each degree of freedom and so that accurate docking and undocking of the test head relative to the peripheral may be accomplished. An example of an electronic test head positioner is disclosed in a previous patent by Smith (U.S. Pat. No. 4,527,942), herein incorporated by reference. This patent discloses a positioner assembly which enables a test head to be in a substantially weightless condition and to move with six degrees of freedom.
In order to provide the six degrees of freedom, the test head may be attached to a cradle assembly, which may be a U-shaped holder for the test head. Cradle assemblies are shown in U.S. Pat. No. 4,527,942, the patent by Smith (U.S. Pat. No. 4,705,447), and the patent by Holt (U.S. Pat. No. 5,450,766). A cradle typically provides at least two of the required degrees of freedom. When a cradle is used to hold the test head, problems have been incurred in easily and quickly locking the cradle into place after it has been docked with the peripheral.